For the treatment of cataracts, it has been the normal practice for decades to replace the natural lens with an artificial lens, a so-called intraocular lens, abbreviated IOL, in the framework of an invasive surgical operation.
Problems may arise after the insertion of the intraocular lens for various reasons, which impair the eyesight of the patient receiving the intraocular lens.
Thus, the refractive correction intended prior to the operation—by the selected inserted intraocular lens—may not actually be achieved after the operation. By way of example, the IOL calculation may have been inaccurate, or the IOL may have shifted during the healing process with regard to its position and/or orientation. This applies to both mono-focal as well as so-called multi-focal intraocular lenses.
Furthermore, it may be the case that after the operation, an implanted multi-focal lens may not be tolerated by a patient, e.g. due to sensitivity to glare.
It may also be the case that after the operation, the patient is not satisfied with the mono-focal intraocular lens, and would like to be able to see at a distance as well as close-up without needing glasses, thus desiring a multi-focal intraocular lens.